The invention relates to a digital watermark method of embedding various information such as copyright, sales date, sales destination, and the like into image data.
The following items are required in a digital watermark function to change a data value of image data and embed information such as a copyright and the like in accordance with a changing method.
(1) The human being cannot perceive a change in image data or can judge that such a change lies within a extent which does not become a problem on use.
(2) Even if a process accompanied with a change in image data value such as a JPEG (Joint Photographic Experts Group) compression or the like is performed to image data in which information has been embedded, the embedded information is hardly extinguished and can be perceived.
In the conventional information embedding technique, as disclosed in xe2x80x9cNikkei Electronicsxe2x80x9d, Vol. 683, pages 99-107, 1997, to satisfy those requirements, a device has been made with respect to the kind of value as a target to be changed. That is, a change is added to the value so that the change is inconspicuous and the embedded information is hard to be extinguished. For example, an image is frequency-expressed and a change is added to coefficients of middle-range values.
The relation between the change in image value and the visual change differs every image and, further, in dependence on a region in the image. For example, in a flat region, even a slight value change is conspicuous, while in a complicated region such as a forest photograph, even a large value change is inconspicuous.
In the above conventional technique, however, a magnitude of the value change cannot be optimized in dependence on the nature of the image. In case of preferentially aiming the prevention of the visual change, therefore, it is necessary to reduce the value change by presuming a case of a flat image and the survivability against an image process is small. In case of preferentially aiming the survivability to the image process, it is necessary to increase the value change and a visual change occurs in a flat image. That is, according to the conventional method, it is difficult to realize both of the prevention of the visual change and the survivability against the image process.
As the related application to this invention, there are JP-A-8-161483, JP-A-10-49669, JP-A-10-49670, U.S. Ser. No. 08/258,382 and JP-A-10-283471.
To solve the above problems, it is an object of the invention to provide a method which can realize both of the prevention of the visual change and the survivability against the image process in a process to embed information into image data.
In the field of a medical image process, a filter to make a diagnosis by the doctor easy for a photograph of the human body photographed by using an X-ray or an MRI is being studied. The most advanced medical filter has the following nature as disclosed in The Transactions of The Institute of Electronics, Information and Communication Engineers, D-II, Vol. J79-D-II, No. 8, pages 1347-1353.
(1) Noises are removed by a smoothing process.
(2) With respect to edge information that is important for the human sight, namely, a portion where an outline of an object or a nature of a plane changes, a shape is preserved.
The present inventors hit an idea to solve the above problems by using the nature of the medical filter mentioned above. That is, the above problems can be solved by an information processing system comprising means for inputting image data and means for embedding information into the image data, wherein a data value of the image data which is imperceptible by the human being or which does not obstruct the reference to the image by the human being is changed by using the medical filter, a range between the value before the change and the value after the change is set to a changeable range of the value in the information embedding, and the information is embedded by changing the data value of the image data within the changeable range.